Correlating Emissions with Time and Temperature to Predict Worst-Case Emissions from Open Liquid Area Sources

Abstract

The two primary factors influencing ambient air pollutant concentrations are emission rate and dispersion rate. Gaussian dispersion modeling studies for odors, and often other air pollutants, vary dispersion rates using hourly meteorological data. However, emission rates are typically held constant, based on one measured value. Using constant emission rates can be especially inaccurate for open liquid area sources, like wastewater treatment plant units, which have greater emissions during warmer weather, when volatilization and biological activity increase. If emission rates for a wastewater odor study are measured on a cooler day and input directly into a dispersion model as constant values, odor impact will likely be underestimated. Unfortunately, because of project schedules, not all emissions sampling from open liquid area sources can be conducted under worst-case summertime conditions. To address this problem, this paper presents a method of varying emission rates based on temperature and time of the day to predict worst-case emissions. Emissions are varied as a linear function of temperature, according to Henry's law, and a tenth order polynomial function of time. Equation coefficients are developed for a specific area source using concentration and temperature measurements, captured over a multiday period using a data-logging monitor. As a test case, time/temperature concentration correlation coefficients were estimated from field measurements of hydrogen sulfide (H2S) at the Rowlett Creek Wastewater Treatment Plant in Garland, TX. The correlations were then used to scale a flux chamber emission rate measurement according to hourly readings of time and temperature, to create an hourly emission rate file for input to the dispersion model ISCST3. ISCST3 was then used to predict hourly atmospheric concentrations of H2S. With emission rates varying hourly, ISCST3 predicted 384 acres of odor impact, compared with 103 acres for constant emissions. Because field sampling had been conducted on relatively cool days (85-90 degrees F), the constant emission rate underestimated odor impact significantly (by 73%).

Occupational asphyxiation by unknown compound(s): Environmental and toxicological approach

“…Therefore, we could suppose that, since the sulfur was shipped in liquid form (sulfur melting point 113 8C), H 2 S easily passes from the liquid to gas phase in the tanker due to its high vapor pressure (252 psi at 21 8C) and low boiling point (À60 8C) (see Table 3). Additionally, its low Henry's constant (8.7 Â 10 À2 M/atm) confirmed its low solubility [38,39] which is similar to those reported for other gases such as O 2 (K H = 1.3 Â 10 À3 M/atm) and CO 2 (K H = 3.4 Â 10 À2 M/atm) [40].…”

Odor Emission Rate Estimation of Indoor Industrial Sources Using a Modified Inverse Modeling Method

“…21,25,30,31 However, none of these studies estimated the accuracy of models used. A comparative study between the CALPUFF model and the ISCST3 Gaussian dispersion models examined downwind odors and source emission rates and concluded that both models are unable to predict peak odor concentrations by using a constant average emission rate, and odor emission rates obtained by back-calculating fluxes using CALPUFF and ISC models with the same field measurements of downwind odor concentrations are significantly different.…”

Gaseous Emissions from Wastewater Facilities

“…Emission rates for a wastewater odor study are measured on a cooler day and input directly into a dispersion model as constant values, odor impact will likely be underestimated. Nagaraj and Sattler (2005) Characterization of the newly synthesized material was performed using BET, XRD, TEM, SEM and DRIFTS techniques, in addition to its carbon and nitrogen elemental composition.…”